Whether you choose to call it adaptive delivery, real-time throttling, rate-limiting, automatic back-off mode, or anything else, the truth of the matter is that delivery policy controls, an advanced and quite sophisticated set of established email delivery technologies, have been a core mechanism of carrier grade MTAs for a few years now. Truth be told, while there have been some qualitative distinctions surrounding delivery policy controls lately; there really haven’t been any “game-changing” technological advancements in the very recent months.

Delivery Policy Controls

To proactively address deliverability challenges in real-time, Delivery Policy Controls allow you to maximize email delivery, and comply with ISP anti-spam traffic shaping guidelines automatically. Senders have the unique ability to optimize delivery settings, on a per domain basis, or more granularly, at an individual mail stream level. Having more control over these settings permits senders to apply specific policies on a per server, per domain, per VirtualMTA, or per campaign basis. One of the essential delivery policy controls is rate-limiting. When an ISP senses erratic sending behavior from a particular IP, or a particular domain, ISPs will exhibit what I call a yield sign (or temporary block) to fully digest incoming traffic patterns, in part due to peak traffic congestion, or network connectivity issues. By assigning control of critical volume parameters, ISPs shape incoming traffic based on simultaneous connections, messages per connection, and active connection retry attempts for just about any given time period. These delivery pylons, when configured and optimized in your sending environment, work to monitor, alert, and most importantly preserve sending reputations.

Justifications

While all senders have their own justifications and policies conducive to their deliverability environments, what’s important to consider is that these delivery policy capabilities have been around and well documented for a few years now. Without a doubt, and despite best practices, a majority of senders still underestimate the potential of this feature to defend and restore sending reputations and dramatically improve inbox deliverability.

Speed Bumps and Traffic Jams

Traffic shaping is of particular interest to ISPs. Their high-cost, high-traffic networks are their major assets, and as such, are the focus of their attention. They often use traffic shaping as a method to optimize the use of their network. Sometimes optimization can be achieved by intelligently shaping traffic according to importance of email stream or client. At other times, it is necessary to discourage or block bad actors. When you imagine all the traffic that ISPs receive, think of a very busy interstate highway. When an accident occurs, the highway patrol has to shut down lanes and literally shape traffic patterns. A five lane highway is quickly whittled down to two lanes and traffic is backed up for miles. Sometimes the traffic slows to a crawl. In almost all cases, the delay causes frustrations in the drivers involved. Similarly, senders become frustrated when networks get clogged by bad actors. If a bad actor congests the ISP network, traffic jams occur, just as they do when an irresponsible driver fails to obey the speed limit and causes an accident. When you think about it, ISPs work the same way as the highway patrol. Not only do ISPs seek to efficiently deliver sends on your behalf, they also encourage and want to preserve your sending reputation. Ultimately, these sets of delivery policy controls, give responsible senders the advanced tools they need to manage traffic jams. Next time you consider escalation to your ISP, understand that the majority of the time, it’s probably temporary, so don’t panic.

Special thanks to Carlo Catajan, ISP Relations and Product Manager for Yahoo who inspired me to write this post.